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gpl

Yup, it's been a while since my last blog post, but I'm not dead yet. Most of my spare time goes into sigrok development these days (open-source signal analysis suite for logic analyzers, oscilloscopes, multimeters, and lots more), but I'll try to revive my blog too. I have various microcontroller/embedded topics and devices I want to talk about in a small blog post series in the nearer future. But more on that later.

Feel free to subscribe to the sigrok-devel mailing list, join us on IRC in #sigrok (Freenode) where most of the discussions take place, or follow our new sigrok blog (RSS) if you're interested in the ongoing sigrok developments. Anyway, for now just a quick announce:

We'll have a sigrok "assembly", likely in area 3b of the conference building, where we'll be hanging around, working on new sigrok features, new hardware drivers, new protocol decoders and various other things. We'll have lots of gear with us for demo and development purposes, including logic analyzers, oscilloscopes, MSOs, multimeters, and lots more.

Chat with us, give us your suggestions which features you'd like to see, which devices you want to be supported, which protocol decoders you'd like to have, or even help us write some drivers/decoders!

The main use-case of the device is to help you recover easily from a failed BIOS upgrade (either due to using an incorrect BIOS image, due to power outages during the flashing progress, or whatever). The device only supports SPI chips, as used in recent mainboards (in DIP-8 form factor, or via manual wiring possibly also soldered-in SO-8 variants). It can identify, read, erase, or write the chips.

Of course the whole "toolchain" of software tools I used for creating the hardware is open-source, and the hardware itself (schematics and PCB layouts) are freely released under a Creative Commons license (i.e., it's an "Open Hardware" device). The user-space source code is part of flashrom (GPL, version 2), the schematics and PCB layouts are licensed under the CC-BY-SA 3.0 license and were created using the open-source Kicad EDA suite (GPL, version 2).

The schematics, PCB layouts, and other material is available from gitorious:

The first few prototype boards I ordered at PCB-POOL.COM (but you can use any other PCB manufacturer of course), the bill of materials (BOM) lists the Mouser and CSD electronics part numbers and prices, but you can also buy the stuff elsewhere, of course (Digikey, Farnell, whatever).

I already hand-soldered one or two prototypes and tested the device. Both hardware and software worked fine basically, you just need a small one-liner patch to fix an issue in flashrom, but that should be merged upstream soonish.

In order to make it easy for interested users to get the PCBs I'll probably make them available in the BatchPCB Market Place soonish, so you can easily order them from there (you do still need to solder the components though). Note: I'm not making any money off of this, this is a pure hobby project.

All in all I have to say that this was a really fun little project, and a useful one too. This was my first hardware project using Kicad (I used gEDA/PCB, also an open-source EDA toolsuite, for another small project) and I must say it worked very nicely. I didn't even have to read any manual really, it was all pretty intuitive. Please consider not using Eagle (or other closed-source PCB software) for your next Open Hardware project, there are at least two viable open-source options (Kicad, gEDA/PCB) which both work just fine.

I've been buying quite a lot of (usually cheapo) gadgets recently, which I'll probably introduce / review in various blog posts sooner or later. Let me start with a fun little gadget, a digital USB-based microscope. I found out about it via this thread over at lostscrews.com.

You can get this (or a very similar device) e.g. on eBay for roughly 50 Euros. Mine seems to be from a company called Oasis (though they're probably just the reseller, not sure). The device doesn't seem to have a nice name, but I can see UMO19 MCU003 on the microscope, so I guess that's the name or model number.

It can focus on magnifications of 20x or 400x. The image resolution is said to be a max. of 1600x1200, but in practice most of my images are 640x480, maybe I have to change some settings and/or the resolution depends on the magnification factor and lighting conditions.

The device acts as a simple UVC webcam when attached to USB, so you can view the images easily via any compatible webcam software, e.g. luvcview and also save screenshots of the magnified areas (see images).

First three from left to right: SMD LED (400x), clothes/jacket (400x), random PCB (20x). The other two below: A via on a PCB (400x), and the "pixels" of a TFT screen (400x).

It worked out of the box on Linux for me, the uvcvideo kernel driver was loaded automatically.

This is a really fun device for having a look at stuff you'd normally not see (or not well enough), and also useful for e.g. checking PCB solder joints, checking all kinds of electronics for errors or missing/misaligned parts, finding the chip name / model number of very tiny chips etc. etc. I can also imagine it's quite nice for biological use-cases, e.g. for studying insects, tissue, plants, and so on.

Anyway, definately a nice toy for relatively low price, I can highly recommend a device like this. Check eBay (search for e.g. "usb mikroskop 400") and various online shops for similar devices, there seem to be a large number of them with different names and from different vendors. Just make sure it has at least 400x magnification, there are also some with only 80x or 200x which is not as useful as 400x, of course.

The deadline for student applications is April 9th at 19:00 UTC, so if you're a student and you want to work on a coreboot (open-source BIOS / PC firmware) or flashrom (open-source BIOS chip flasher) project, please apply in time.

I guess it's time to finally announce libopenstm32, a Free Software firmware library for STM32 ARM Cortex-M3 microcontrollers me and a few other people have been working on in recent weeks. The library is licensed under the GNU GPL, version 3 or later (yes, that's an intentional decision after some discussions we had).

Building is done using a standard ARM gcc cross-compiler (arm-elf or arm-none-eabi for instance), see the summon-arm-toolchain script for the basic idea about how to build one.

The current status of the library is listed in the wiki. In short: some parts of GPIOs, UART, I2C, SPI, RCC, Timers and some other basic stuff works and has register definitions (and some convenience functions, but not too many, yet). We're working on adding support for more subsystems, any help with this is highly welcome of course! Luckily ARM stuff (and especially the STM32) has pretty good (and freely available) datasheets.

The current list of projects where we plan to use this library is Open-BLDC (an Open Hardware / Free Software brushless motor controller project by Piotr Esden-Tempski), openmulticopter (an Open Hardware / Free Software quadrocopter/UAV project), openbiosprog (an Open Hardware / Free Software BIOS chip flash programmer I'm in the process of designing using gEDA/PCB), and probably a few more.

If you plan to work on any new (or existing) microcontroller hardware- or software-projects involving an STM32 microcontroller, please consider using libopenstm32 (it's the only Free Software library for this microcontroller family I know of) and help us make it better and more complete. Thanks!